Why Miracles Are Possible: David Hume and the Reasonableness of Belief

For millennia the issue of miracles has been central in many religions, especially in Christianity. But in the eighteenth century philosopher David Hume changed the West’s entire understanding of miracles. Hume argued that people should, as a practical matter, always disbelieve miracles and be skeptical of them because any amount of testimony or proof is always outweighed by the universal human experience of the laws of nature. Hume’s argument relies on the premise that the laws of nature are actually known to human beings. Yet this proves to be problematic because humans do not have full knowledge of nature’s laws and so cannot confidently assert that miracles are impossible. Could it not be that the law of nature itself includes within it exceptions or deviations that seem to violate nature’s usual behavior? The truth is we do not know, and no matter how much empirical evidence we gather we will never be able to say that we, as humans, know the absolute truth about what the law of nature is. After all, our human reason has its own limits. In Hume’s other writings, even he emphasizes the limits of human reason in our understanding of nature, law, and causality. Based on those limits, I argue not that this miracle or that miracle happened, or that miracles come from a divine being, but simply that it is reasonable to believe that miracles are possible.

The term ‘miracle’ is used rather loosely today. To avoid confusion, I want to clarify that there are two types of miracles. The first type can be defined simply as a rare and improbable event. For example, a woman surviving a terrible car accident could be described as a ‘miracle’ – in other words, very unlikely and amazing. The second type can be defined as something that seems to contradict human understanding of the laws of nature. An example of this would be Lazarus rising from the dead as reported in John 11:38-44. I am focusing only on this second type of miracle.

Hume’s argument against miracles can be understood in two parts: a moderate one and a radical one. The moderate claim is that miracles are unlikely, so we should be slow to believe them. The radical claim is that miracles are essentially impossible, so we should never believe them. The moderate part of Hume’s argument is unobjectionable. Hume writes that the burden of proof for any miracle lies on the person who is claiming to have performed or witnessed the miracle.[i] This simply means that we should be reluctant to believe in this or that miracle. If anyone asserts that the human understanding of the laws of nature has been violated in a certain instance, then of course a heavy burden of proof should be placed upon that person.

Most religious believers would agree with Hume on this, as I do. Christianity has no problem with regarding the laws of nature as stable, predictable, and regular. Miracles, whether they seem to violate the laws of nature or whether they are due to divine intervention or chance, are always, by definition, extremely rare. This is why they produce wonder: because we expect nature to be predictable, and miracles disrupt that predictability. For instance, we expect blind people to remain blind, and therefore a miracle that enables a blind man to see inspires wonder and amazement. If there were no predictable laws of nature, then everything would be miraculous and miracles would cease to be extraordinary. So the Christian belief in miracles is not an attack on nature’s laws; it is an affirmation of them. Because miracles are extremely rare in and of themselves, significant testimony and proof is required.

In Hume’s An Enquiry Concerning Human Understanding, he establishes that the number of witnesses should be taken into account along with the validity of the accounts. This constitutes his moderate argument. His conclusion, however, is radical. His conclusion is that no matter how much evidence or testimony you have in favor of a miracle, you should always be skeptical of it occurring because it defies the laws of nature. So in effect, he is saying that you should never believe that any miracle is possible. For instance, if someone says that a dead person has been raised to life, it does not matter how reliable the witness of the event is because universal human experience attests that when we die, we die. Therefore, it is much more likely that the witness is lying or mistaken than it is that the known laws of nature have been violated. Hume even goes further to assert that the only miracle occurring at all is people believing in miracles even when they defy nature’s laws.[ii]

Even though Hume’s conclusion seems radical, there is a practical truth in what Hume says. Obviously we rely on the uniformity of human experience in the way that we live our daily lives. For example, it would be difficult to function if we expected gravity to apply today but not tomorrow. In an attempt to support Hume’s argument, philosopher J.L. Mackie argues that people should not believe in miracles because nature is a closed system and a miracle would represent an intervention into that closed system.[iii]

Yet there is a powerful objection to Hume’s argument against miracles. Here we need to turn to Hume’s epistemology – his theory of knowledge. In Hume’s A Treatise of Human Nature, we find Hume giving us the tools to refute his own argument. He provides a powerful argument for contesting the notion that the laws of nature are fully known.[iv] The effect of Hume’s argument is to demonstrate, not that there are no laws of nature, but rather that as human beings we can never with certainty know what these laws are. Of course, by drawing on human experience we can formulate generalizations that we treat as laws. Science is probably the most reliable collection of such generalizations. Even so, none of those generalizations or laws are “nature’s laws.” Rather, they are human laws, which are nothing more than aggregate observations. These observations merely represent what we have experienced or tried before.

Consequently, Hume’s epistemology itself demonstrates the profound limits of human knowledge. Since we know so little about nature’s laws, we are simply not in a position to say what nature forbids. Just because miracles violate what we know about nature does not mean that miracles violate nature’s laws. The laws of nature that we think are absolute may in fact be “local” laws that only apply in certain realms or domains. Or it could be that there are simply exceptions to certain laws, as C.S. Lewis argues.

But mere experience, even if prolonged for a million years, cannot tell us whether the thing is possible. Experiments find out what regularly happens in Nature: the norm or rule to which she works. Those who believe in miracles are not denying that there is such a norm or rule: they are only saying that it can be suspended. A miracle is by definition an exception.[v]

Let us consider some of the known laws of nature. Light travels at the speed of 186,000 miles a second in a vacuum. Newton’s inverse square law says that objects attract each other with a force proportional to their mass and inversely proposal to the square of the distance between them. There are innumerable other laws. Now it was Hume who pointed out that from no amount of empirical generalizations, however large, can we draw a general conclusion that is true as a matter of fact. Hume says that we presume that there are laws because we assume causation. “By means of that relation,” Hume writes, “we can go beyond the evidence of our memory and senses.”[vi] In reality, as Hume shows, there is no proof of causation; there is simply the repetition of experience. Since scientific laws are themselves empirical generalizations, Hume’s statement applies to all such laws. The stunning implication is that scientific laws cannot be verified in the sense of confirming them to be true in all cases. Scientific generalizations can at best be proven false; they can never be proven true.

We “know” that light travels at speed “c” (i.e. 186,000 miles per second) because we measure it. But even if we measure the speed of light a thousand times, or a million times, it does not follow that light always and everywhere travels at that speed. Possibly on a star many light years away, light travels at a different speed. We presume that this is not the case, but there is no way to know that. We simply cannot measure light often enough and in every place in the universe, so we cannot truthfully say we “know” light always travels at speed “c.”

The philosopher Bryan Magee notes that for centuries in the West, people used the phrase “white as a swan.” That is because all observed swans were white. And this generalization was supported by literally millions of examples. Every swan previously seen was white. Consequently, there are innumerable poems and stories that use the phrase “white as a swan.” Yet when Europeans first set foot on the continent of Australia, they encountered black swans. Suddenly the generalization “white as a swan” no longer held. And how many black swans did it take to defeat the rule? Just one.[vii] Drawing on the lesson of Hume, philosopher Karl Popper noted that science cannot prove anything. The best that science can do is disprove theories.[viii] What follows is that scientific laws are nothing more than generalizations that have so far held true.

By showing the limits of human reason, Hume demonstrates that the known laws of nature are nothing more than what human experience has shown to this point. But science itself is constantly revising and updating itself based on new discoveries and new experience. Even this experience represents the most up-to-date human understanding, yet one that is itself subject to revision and correction. Ultimately Hume uses reason to show how little we can be confident in actually knowing. So miracles cannot contradict the known laws of nature because, quite frankly, there are no known laws of nature. The same point was made by the philosopher Immanuel Kant. “I must therefore abolish knowledge,” Kant wrote in his Preface to the second edition of the Critique of Pure Reason, “to make room for belief.”[ix] Kant is saying that beliefs that go beyond reason should not be dismissed because reason itself is limited and circumscribed. What this means for our purpose is that there is nothing unreasonable in believing that miracles can occur. This does not mean that any particular miracle is true or even likely. Each miracle report must be evaluated on its individual merits – by examining the historical or eyewitness evidence that is given to support it.